1. Field of the Invention
The present invention relates to a real-time simultaneous measurement system and the like for synchronously acquiring information, such as NIRS measurement information (similar to “hemoglobin information” described below) and EEG measurement information (similar to “brain wave information” described below), and outputting the information.
2. Description of Related Art
Conventionally, there is an apparatus that measures brain activity using the NIRS (near infrared spectroscopy) method (see JP 2003-322612A (p. 1, FIG. 1, etc.), for example). Hereinafter, the NIRS method will be described.
Hemoglobin functions as a carrier of oxygen in blood. The concentration of hemoglobin contained in blood changes according to the expansion and contraction of blood vessels. Thus, it is known that the expansion and contraction of blood vessels can be detected by measuring the hemoglobin concentration.
Thus, there is a known biological measurement method that easily and non-invasively performs measurement inside a living body using light, based on the fact that the hemoglobin concentration corresponds to oxygen metabolism inside a living body. The hemoglobin concentration can be obtained by irradiating a living body with light having a wavelength from the visible light area to the near infrared light area and measuring the amount of light that passes through the living body.
Moreover, hemoglobin binds to oxygen to form oxyhemoglobin. Furthermore, hemoglobin without the bound oxygen forms deoxyhemoglobin. It is also known that oxygen is supplied to a section that is activated by a blood flow redistribution action inside the brain, and the concentration of oxyhemoglobin that has bound to oxygen increases. Thus, measurement of the oxyhemoglobin concentration can be applied to the observation of brain activity. Oxyhemoglobin and deoxyhemoglobin have different optical absorption spectra from the visible light area to the near infrared light area, and, thus, the oxyhemoglobin concentration and the deoxyhemoglobin concentration can be obtained, for example, using near infrared light.
Thus, an optical biological measurement apparatus has been developed that includes a light-transmitting probe and a light-receiving probe in order to non-invasively measure brain activity. In such an optical biological measurement apparatus, the brain is irradiated with near infrared light using a light-transmitting probe disposed on the scalp surface of a test subject, and the amount of near infrared light emitted from the brain is detected using a light-receiving probe disposed on the scalp surface. Near infrared light passes through scalp tissues and bone tissues, and is absorbed by oxyhemoglobin and deoxyhemoglobin in blood. Thus, if the light-transmitting probe and the light-receiving probe are used to obtain information on the amount of light received, the oxyhemoglobin concentration and the deoxyhemoglobin concentration in the measurement section in the brain and a time-series change for all hemoglobin concentrations calculated based on these concentrations can be obtained as measurement data. Accordingly, activation of the brain can be measured. Measurement of brain activity performed by this sort of optical biological measurement apparatus is referred to as the NIRS method.
Furthermore, conventionally, there is an apparatus that measures brain activity using the EEG (brain waves) method (see Sadao Ichijo et al., 101 Chapters Regarding Reading of Brain Waves, Igaku-Shoin Ltd., May, 1999, for example). Here, EEG stands for “electroencephalography”, and refers to brain waves. The EEG is a method with which an electrical change inside the brain derived from brain activity can be safely detected from the outside as a potential difference on the scalp.
Furthermore, conventionally, there is a head instrument for EEG measurement at the head portion (see JP H5-261076A (p. 1, FIG. 1, etc.), for example).
However, conventionally, NIRS measurement information and EEG measurement information cannot be synchronously acquired, and the NIRS measurement information and the EEG measurement information cannot be synchronously displayed in real time. Accordingly, there is a problem in that the state of brain activity cannot be determined in real time using NIRS and EEG. More specifically, conventionally, a change in blood flow and an electrical signal derived from brain activity cannot be measured simultaneously and in real time, and the brain state cannot be sufficiently determined.